


Ob Fluctus Eorum

by MidnightNinja27



Category: Kuroshitsuji | Black Butler
Genre: Alternate Universe - Creatures & Monsters, Alternate Universe - Modern Setting, Alternate Universe - Modern with Magic, Cannibalism, Canon Disabled Character, Crossdressing, Cyclops - Freeform, Cyclops Maurice Cole, Daddy Kink, Dark Ciel Phantomhive, Disabled Character, Disabled Sieglinde Sullivan, F/F, F/M, Fae & Fairies, Fae Alois Trancy, Fae Lawrence Bluewer, Female Grell Sutcliff, Female Pronouns for Grell Sutcliff, Foster Care, Hate Crimes, High School, Human Angela Blanc, Human Ash Landers, Human William T. Spears, Human/Monster Romance, M/M, Male Lactation, Mental Conditioning, Mpreg, Murder Kink, Obsessive Behavior, Orphanage, Pavlov’s Dog, Pheromones, Possessive Sebastian Michaelis, Pseudo-Incest, Selkie Grell Sutcliff, Selkies, Singing, Siren Ciel Phantomhive, Sirens, Slurs, Teacher Claude Faustus, Teacher-Student Relationship, Teenage Ciel Phantomhive, The Odyssey References, Unicorn Elizabeth Midford, Unicorns, Vampire Claude Faustus, Vampire Edgar Redmond, Vampires, Wendigo Sebastian Michaelis, Wendigos, Werewolf Herman Greenhill, Witch Gregory Violet, Witch Hunts, Witch Sieglinde Sullivan, Witches, Yandere Sebastian Michaelis, against monsters, boys with boobs, but only references
Language: English
Status: In-Progress
Published: 2021-01-26
Updated: 2021-02-13
Packaged: 2021-03-18 08:00:55
Rating: Mature
Warnings: Graphic Depictions Of Violence, Underage
Chapters: 4
Words: 4,091
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28988910
Author URL: https://archiveofourown.org/users/MidnightNinja27/pseuds/MidnightNinja27
Summary: AU: Modern, Monster VerseA merman found a swimming boy, picked him for his own, pressed his body to his, laughed; and plunged down, forgetting that even love can drown.Sixteen year old Ciel Phantomhive is an orphan living in London when he is selected to be fostered. The couple that chooses him is a human woman and a male wendigo who think they are adopted a human boy. What no one except Ciel knows is that he is a siren, the most feared of all monsters. When he falls in love with his foster father, his biggest secret becomes his greatest asset.The title is Latin for "Unforgiving Waves".
Relationships: Angela Blanc/Ash Landers, Angela Blanc/Sebastian Michaelis, Claude Faustus/Alois Trancy, Elizabeth Midford/Sieglinde Sullivan, Sebastian Michaelis/Ciel Phantomhive, William T. Spears/Grell Sutcliff
Comments: 5
Kudos: 51





	1. Boring Old Life

**Author's Note:**

  * For [Dawnlightsilhouette](https://archiveofourown.org/users/Dawnlightsilhouette/gifts).



Narrator's POV

Sirens were not the creatures everyone thought them to be.

While they did thrive in the water, they thrives just as much —if not more— on land.

They were not mermaids, most of them would never call the ocean home.

But what the folktales had true was one things: sirens had lovely voices.

Centuries ago before creatures and humans got along, sirens were known to lure sailors into the sea to mate with them before eating them.

In the modern era where everyone mostly worked together, sirens were feared.

They were the rarest creature and they could be found one of two places: on the arm of the rich and/or famous or on the arm of the most notorious killers.

Nothing was more attractive to a siren that power and bloodlust, though it seemed nowadays it tended to mostly be the former.

But, to be safe, all of the world's governments had a watchlist of all known sirens to make sure they did not end up with a killer.

***

Sitting in a Co-Creature Group Home in London, Ciel Phantomhive hummed a bit as he stared out his bedroom window.

He loved singing but he never got to do it without revealing his secret.

Hearing the door to his bedroom open, he turned to see his best friend and roommate: Alois.

Alois Trancy was a fae, a creature known for mild magical powers and mischievous attitudes.

Said blond was also one of the three people who knew he was a siren.

"Hey." Ciel greeted, giving his friend a smile, "How did your 'extra credit' go?"

Alois giggled, "I think it went well, Professor Faustus was very pleased with how I can use my hands...helping him grade papers of course."

"Of course." Ciel laughed, "Did he tell you what chapter the pop quiz was supposed to be in? I don't feel like reading all three he assigned."

"Always so practical, always thinking about homework." Alois sighed, "But yeah, he said it is mostly about the second half of chapter twelve."

"Nice." Ciel replied, opening his history textbook to that chapter

Alois sighed playfully, "Sometimes I think you are only my friend so I can get you teacher secrets."

"Well how else was I suppose to get my grade pulled up from an 87 to 95 without your expertise with Faustus after I bombed that project?" Ciel laughed

They both knew t he other was messing around, they had been best friends ever since they were made roommates at age five, about eleven years ago.

Now, they were both sixteen and they agreed on practically everything: including their interest in older men.

Alois had set his sights on Professor Faustus who was a vampire, the blond loved his dark aura and authoritative personality.

Ciel did not see what made it so attractive, personally, but he understood the appeal.

No, what he wanted was different.

Like almost every siren that came before him, he wanted a powerful man.

But unlike most other living sirens, Ciel wanted a killer or someone he could shape into a killer and he would not settle for less.

***

The following morning, Ciel and Alois got dressed for school.

Weston High was pretty strict on its dress code: white button-ups, navy blue blazers, grey and royal blue plaid tie and black leather shoes.

The only real customizable part of it was the bottoms, either navy blue slacks or grey and royal blue plaid pleated skirt with white stockings.

Both boys were proud crossdressers so they went with the latter option.

Ciel was a rather mild crossdresser compared to Alois who completed his look with a bit of makeup Claude had bought him.

Though —like everyday— the slightly older boy insisted he wear some pale pink lipstick to pull the look together, so he did.

Once dressed, they went downstairs to the dining room to eat with the rest of the orphans.

The pair sat in their usual seats beside their other besties: Elizabeth Midford and Sieglinde Sullivan.

Lizzy was taller than both of them by several inches, but her cotton candy pink horn on the center of her forehead made her look even taller than she was.

She was not part horse like a centaur —hardly any unicorns were anymore after so much breeding with humans— the only horse-like aspects she had was her horn, mild magic and tail as well as her love for apples and sugar cubes —but that was mostly a joke she had with her friends.

Her golden blonde hair were in their usually curly pigtails —and her tail was just as curly— the curls were dip-dyed the same pink as her horn.

And of course, she was dressed identically as them.

Beside Lizzy was her girlfriend and roommate, Sieglinde.

Sieglinde was a witch and had lived in the orphanage longer than the others in their friend group.

When she was an infant, her coven was attacked and killed by witch hunters and she had been the only survivor, but her feet had been deformed during the attack so she was wheelchair bound.

Besides sirens, witches were teh group that faced a lot of prejudice because of all the human stories and slander.

The much smaller girl —barely taller than Ciel— had black hair styled into horns and was dressed identically as them.

Soon, the orphanage matron walked into the dining room carrying a tray of food.

Grell Spears set the tray of food on the center of the table.

Madam Spears was a selkie with long red hair, green eyes, and was never seen without her crimson selkie coat or red glasses.

On the tray was a bowl of fruit and a platter of pastries.

Walking into the room was Mister Spears.

William was a human, he had brown hair and the same yellow green eyes as his wife.

He was also carrying a tray of food, this one holding tubs of bacon, scrambled eggs and fried potatoes.

All of the ten kids in the group home began to pile their plates high with food...


	2. Weston High School

Narrator's POV

After breakfast, William went to every one of the ten orphans and gave them their monthly allowance of ten pounds —it was not a lot, but it was what they could spare to let the kids learn about money management.

With that done, Grell got all of the kids into the van and drove them to their schools while William was heading off to work.

***

Ciel walked into the local high school with his friend behind him like he did everyday.

As they entered the old building, Lizzy and Sieglinde went towards the elevator, the former escorting the latter to the genius classes before rejoining her friends.

While Alois and Ciel waited for Lizzy to return, they went to the library like usual.

Unlike usual, when they arrived there was five people already sitting at their table.

Naturally, it was the five worst bullies kids in school who were all rich and popular.

The most mild of the five were Gregory Violet —a witch— and Lawrence Bluewer —a fae— who did little more than stand by and laugh whenever their friends bullied someone.

The three of them who were not mild were Edgar Redmond —a vampire—, Herman Greenhill —a werewolf— and the worst of all: Maurice Cole, who was a cyclops.

The one-eyed blond laughed when he saw Ciel, "And here I was thinking that I was the one with the worst eyes in school."

Ciel scowled, his heterochromatic lavender and blue eyes looking into Maurice's one green eye.

The hidden siren knew even part of a song would be enough to get the bully off his back for good but he held strong, he wouldn't risk his future due to a jerk.

"At least I have two eyes." Ciel shot back, "So maybe you have it worst than some Nobody like me."

Maurice growled at the Odyssey reference, that entire tale was slander against Cyclops by making them seem dumb and humans smarter.

Alois then led Ciel out of the library before things could escalate, running into Lizzy in the hallway.

Together the three of them walked to their classes.

***

At lunch, Ciel was standing in the lunch line with Lizzy and Sieglinde —Alois having lunch with his teacher boyfriend.

Today it seemed his friends were very interested in finding him a boyfriend.

They kept pointing to various guys of all sorts of species from orc to human to vampire.

Ciel denied them all, always finding a flaw with them from too dumb, too unattractive to just too boring.

He wanted a very specific type of man and as much as he appreciated his friends trying to help him, that type of guy was not here.

***

After school, the four of them waited at the front of the school for Madam Spears to pick them up.

They sat on the cement walkway in front of the school playing go fish with their falling-apart playing cards.

Not really paying attention to the world around them, the four of them barely even noticed the car park beside them on the road.

“Hey, freakshow!” A voice called out

The four orphans turned around, seeing Maurice in his goon’s sitting in Edgar’s red corvette, the convertible roof down.

Ciel rolled his eyes, seeing the group home’s van approaching.

“Says the one who sucks off four men for attention.” Ciel shot back, “I bet they have to blindfold you to get it up.”

With that said, the four of them then went to the van before the populars could retaliate.

***

Upon arriving back at the group home, the four best friends began to head to the common room but Mister Spears stopped them, “Mr. Phantomhive, please step into my office, I need to speak with you.”

Confused as he had not done anything wrong, the blunette did as told.

“What’s going on, sir?” Ciel asked as William sat at his desk

“You are being transferred to another facility.” William explained, “You-“

“What!? No! I like it here.” Ciel protested, interrupting

William spoke again, “You would not be leaving the city, not even the school district. A mixed species couple is interested in fostering a human teenager and you are the only one we have.”

“What about Ellery Nixon?” Ciel suggested, not wanting to go, “She is human.”

“She is also ten years old, the foster parents requested a teenager.” William retorted, “J am sorry, Ciel, but you are the only one who fits their request. Who knows, maybe things will go well and they might even adopt you.”

Ciel pouted, he knew that was a long shot: no one ever adopts a teenager, especially one like him about to age out of the system.

“Call them and tell them I am not going. I am aging out in six months, I would like to spend my time here with my friends.” Ciel angrily said, standing up and leaving the room

***

Slamming his bedroom door closed, Ciel barely kicked off his shoes before plopping into bed.

“What’s wrong?” Alois asked, concerned, “Did Spears say something?”

Still hiding his face against his pillow, Ciel groaned, “Some couple wants brownie points by fostering a teenager, a human one.”

“That is such bull.” Alois agreed

“Spears said they live nearby so I wouldn’t be going far but still, I am happy here.” Ciel complained

Alois shrugged, “Maybe that would not be so bad. Maybe they would be nice and you would get a bigger allowance or new stuff.”

“Or they could be arses looking for an easy paycheck and not give me anything.” Ciel argued, “And it messes with our plan.”

The blond fae just nodded, for the past few years they had all agreed that when they aged out they would rent an apartment together and share everything.

Though that planned changed when he got involved with Claude and would be moving in with him after graduation.

“Who says it will change that much, if they are as bad as you think then they will just kick you out in six months anyways and we can continue like always.” Alois suggested...


	3. A New Home

Narrator's POV

It seemed William had not listened to him because the following day Ciel was called into said man's office.

When Ciel walked into the small office, he was greeted with the sight of two people.

The first was a human woman with platinum blonde hair cut into a bob and lavender eyes, she was wearing a navy blue business suit set and matching heels.

She was likely had a giant ancestor because she was extremely tall, probably around seven feet tall.

But she was not what caught Ciel's attention, it was the man beside her who caught it.

The man was clearly a wendigo; he was absolutely giant at ten feet tall.

He was ghostly pale, but his hands neck, and what could be seen of his torso and arms were covered in pitch black scales.

His fingers were tipped in sharp claws, his teeth were sharp fangs.

He had messy yet neat black hair remaining his crimson eyes, his head were topped with antlers and ram-like horns.

The wendigo wore a crimson T-shirt and black leather jacket, along with dark grey jeans and black Dr Martens.

Ciel found him incredibly handsome and immediately thought, "I want him."

"Ciel, meet Angela Blanc-Michaelis and Sebastian Michaelis, your new foster parents." William introduced

The blunette frowned, putting up a show of anger, "Hi."

He then sat there while the adults did the paperwork for him, eventually being told to go pack his things.

Ciel only had one duffle bag, so he stuffed all his clothes and things into it, carrying his stuffed animal —Bitter Rabbit.

He gave each of his friends a hug snd promised to see them at school on Monday.

***

Before long, Ciel found himself sitting in the back of a black Jeep.

Both of his foster parents sat up front, the human of which began talking him.

"We are so glad to have you, Ciel, we want to take care of you and let you be a normal teenager. As long as you follow the few rules of the house we won't interfere too much." Angela explained

Ciel rolled his eyes, "What are the rules?"

"1. No cursing and be polite. 2. Do your homework and whatever chores we give you. 3. No bringing people home." Angela informed

That seemed easy, so Ciel asked, "What would the chores be?"

"Just average things like loading the dishwasher, taking out the rubbish, folding laundry, stuff like that." Angela explained

Before long, Sebastian parked the car in front of a house in a upper-middle class neighborhood.

The house was on the edge of a thick forest and his new foster parents gave him a tour around the house before finally showing him his bedroom.

His new bedroom was huge compared to the one he shared with Alois, it had a full sized bed, a desk, a balcony and a en suite bathroom.

"This is all for me?" Ciel asked, amazed at all the space

"Yes." Sebastian confirmed, "We'll be giving you five hundred pounds to decorate."

Ciel's mismatched eyes bulged a bit, he had never had that much money before.

He did not even believe it as ten fifty pound notes were placed into his hand.

The two adults then left him alone to do his homework and said they would call him down for dinner.

***

Dinner came faster than Ciel expected, taking him time setting up his belongings.

He went down the stairs and entered the kitchen where he found Sebastian cooking.

"Hello, Ciel." The wendigo greeted, placing two steaks on the griddle while leaving the third and largest on the cutting board, "How would you like it cooked?"

"Medium rare." The teen replied, "Would you like any help cooking?"

"Not really, unless you would like to set the table?" for shrugged

"I can do that." Ciel smiled, secreting a bit of pheromones

He had to be careful, if he released too many Angela —who was sitting in the living room watching television— would smell them too.

And, he was not interested in a polyamorous relationship —or women in general— so he did not want that at all, so he just needed enough to get Sebastian’s attention and keep it.

Ciel knew his plan worked, seeing how the wendigo kept shifting in his seat to keep his arousal hidden.

The blunette knew he was beautiful —it was genetically impossible for a siren not to be— but he knew his wardrobe certainly helped.

His bottom-ware was made up of miniskirts and short shorts exclusively —not a single pair of pants anywhere, excluding the tights he had but those were lace or fishnet so that did not really count— and his longest skirt was the one to his uniform but even that just barely managed to cover his bubble butt.

His thighs were thick with two c’s and his lips had always been described as pouty.

And well, sirens had a little secret in their trade: they could alter their bodies.

Not nearly as much as a true shapeshifter, but enough to alter themselves to make themselves fit into the current beauty standard —and give themselves mermaid tails so they could live at sea if needed, but that was not the point.

If he wanted to he could also transition fully into a girl with little more than a thought —as sirens were once an exclusively female species before they began breeding with nonhumans— but he would not as he enjoyed being male.

Perhaps he would give himself breasts later, Angela had a rather large set and if he was competing with her he needed to surpass her.

But first he had to learn where her Sebastian preferred arses or breasts —every male had a favorite.

***

The next day, Ciel walked back to the mall and began shopping for stuff to decorate his room.

He bought posters, fairy lights, light up stars for the ceiling that were real constellations, tarot card tapestries, a moon shaped dreamcatcher and so much more.

The teen even bought a whole bunch of stuffed animals to accompany his Bitter Rabbit.

He took his bags of decor to his new home and decorated his empty room.

This was something he could get used too...


	4. A Date to Remember

**Notes for the Chapter:**

> If you request meat to be cooked ‘blue’ it means so rare it is practically raw, so Sebastian is not asking for a blue piece of meat.

Narrator's POV

The weeks that passed were dreadfully boring: school went on as usual, Ciel adapted to his new routine and his infatuation with his foster father grew.

The siren's lucky break came during the week before the spring break —when he would be out of school for a full week— because he learned that Angela would also be out of town on a business trip during the break.

But that was still a week away, so Ciel sat in his bedroom on his brand new laptop Sebastian had just got him for schoolwork.

His brand new iPhone buzzed as he received a text message, checking it he saw the text was from the group chat he was in with his foster parents.

Angela had written that she would be working late tonight and wouldn't be back until the AMs.

Ciel smiled and closed his laptop, maybe he could not fully seduce Sebastian until the break, but perhaps he could get a kiss tonight.

Closing his laptop and heading downstairs, Ciel found Sebastian in his home office typing at his computer.

"Hey, daddy." Ciel greeted, "Whatcha doin'"

"Just some paperwork." Sebastian sighed

The teen had started calling Angela 'mom' snd Sebastian 'daddy' recently, so the wendigo did not notice the sweetness packed behind the nickname.

Nor did he notice the sickly sweet smell of the pheromones, he just noticed how hard he was suddenly.

"Sounds boring, daddy." Ciel said, sitting on his lap, on top of his arousal, "Let's go have some fun tonight, let's go out to eat and maybe see a movie."

Sebastian's mind was cloudy, his judgment not realizing he was being asked out on a date, "Yes, that sounds fun."

The siren kissed the wendigo's cheek, "Perfect, I will go get dressed."

***

Ciel hurried back to his bedroom and walked into his closet, pulling out his two favorite dresses: one was very sexy and bold, the other was homely with a sexy flair.

Deciding upon the first dress as he would have plenty of time to look like a housewife when Angela was out of the way, he got dressed.

The dress he picked out was covered completely in black lace, had a deep sweetheart neckline and illusion sleeves.

The skirt was very short on the front, leaving his thick thighs and slender legs on display but the back of the skirt brushed the floor.

Going over to his vanity, he applied a bit of makeup, not enough to mask his natural beauty but a bit to elevate it.

Ciel applied a bit of contouring to his chest, making the tiny AAA breasts he gave himself have more definition.

After all, people would notice if he suddenly had giant breasts out of nowhere, so he needed to build them up slowly.

He then hooked a string of pearls around his neck and clipped a lacy black bow into his hair.

Slipping his petite feet into lacy black heels, he made his way down the stairs.

***

When he arrived at the front door where the wendigo was waiting, Ciel watched as Sebastian’s mouth gaped.

“Y-You look beautiful.” Sebastian stuttered

Ciel blushed, “You think so? You look handsome too.”

And the wendigo did in his grey button up, black slacks and black suit jacket.

“Where are we going to eat?” The blunette asked as they walked out of the house and to the car

The black haired creature unlocked the vehicle’s door, opening the passenger door to let Ciel in first, “A steakhouse I enjoy.”

***

The drive was short, about twenty minutes, until they arrived at a fancy looking steakhouse.

A hostess —who was a pixie, barely a foot tall and fluttering through the air as she led them to their table— and snapped her fingers once they were sitting to give them the omnivore and carnivore menus.

After all, every restaurant —unless they catered exclusively to one group— had to have three menus for humans and other omnivore creatures, carnivores like wendigos and werewolves, and herbivores like unicorns and nymphs.

The pixie then left and their waitress —who was a harpy, her bird talons tapping against the tile floor as she approached, her eagle wings folded against her back.

“Hello, what would you like for refreshments?”

Both of them requested water, so the waitress then asked if where ready to order any appetizers.

Sebastian did not even glance at the menu, he knew what he wanted, “Venison tenderloin.”

“How would you like that cooked?” The harpy questioned

“Blue.” The wendigo replied

“I would like oysters on half shell, please.” The teen said, picking something more grand now that he new Sebastian was not being frugal

She then left to place their order, giving them a chance to talk.

“This is a really nice place, daddy.” Ciel began, starting the conversation, “You seem to be really familiar with the menu, do you come here a lot?”

“I used to.” The other male m replied, “Angela and I came at least once a month until work began swamping her.”

The teen internally smirked, that was an opening he could squeeze into, so she pouted, “She can not even make room for one evening out with you? That is so horrible.”

“It is fine, I enjoy cooking anyways.” Sebastian shrugged, trying to play it off

The hidden siren gave him his sweetest smile and placed his hand on top of the wendigo’s, stoking his clawed fingers with his delicate ones, “We could continue that tradition, daddy, you could take me in her place here every month. Just you and me out to a nice dinner, then maybe to a movie or a play.”

“That sounds nice.” Sebastian smiled

The rest of the meal was wonderful: Sebastian got a prime tomahawk steak that was also blue for his entree, Ciel got crab cakes for his meal.

Dessert was delicious as well, Ciel got a tuxedo cheesecake for dessert while Sebastian got Sanguinaccio dolce —an Italian pudding made with blood, fruits, nuts and a bit of milk and chocolate.

Over all, it was a wonderful night, even though Ciel did not get the kiss he craved...

**Notes for the Chapter:**

> In honor of me being seemingly eternally single, there was a date night fit for Valentine’s Day.


End file.
